Many portable electrically powered devices use electrical storage batteries as a source of electrical current to energize electronic circuitry and electrical motors included in the devices. The batteries are typically disposed within a battery compartment formed in a housing or enclosure of the device. It is common to secure the batteries in a battery compartment of a portable device with a cover having tabs disposed along its periphery that engage the sides of the compartment opening or fit into slots disposed adjacent the edges of the opening. Since housings and battery compartment covers are frequently made of plastic to ensure low cost and light weight, it is not uncommon for the tabs on the battery cover to break with usage or become ineffective in securing the cover in place.
For some types of portable devices, it is important that the housing be either watertight, or at least water resistant. A simple snap-in-place battery compartment cover is generally not capable of providing even a water resistant seal. One solution to this problem is to use a cover that is threaded into mating helical threads formed in the opening of the battery compartment and which includes an "O-ring" that is compressed when the cover is tightened, to form a watertight or at least a water resistant seal. However, threaded covers are much less convenient to remove and replace than snap-in-place battery compartment covers. In addition, some types of plastic used for housings do not have the proper friction characteristics to perform well when threaded into engagement with a mating threaded part. Accordingly, it would be desirable to provide a cover for a battery compartment that effects a watertight seal with a housing, but which is readily removed and resealed following servicing of the batteries. Such a cover should preferably be formed of plastic or other low cost material, but should not be easily broken.
A specific application for such a cover exists in connection with sealing a battery compartment in an ambulatory infusion pump. Because some users may need to use the infusion pump in wet environments, e.g., while taking a shower or bathing, it is important that the housing be watertight. Prior art ambulatory infusion pumps have not provided a watertight seal for the battery compartment and thus have enabled water to leak into the interior of the housing, causing damage to internal electronic circuitry and components. A need for a simple, easily usable watertight battery compartment cover has led to the development of the present invention. No prior art battery compartment cover is known that meets all of the requirements noted above.